In the drilling of bore holes utilizing an in-hole motor, such as an in-hole positive displacement fluid motor or a fluid turbine, drilling thrust is applied to the drill bit through a shaft which is connected to the rotor of the motor. Bearings are provided which transfer the drilling thrust to the shaft from a housing which is connected to the stator of the motor. Other bearings thrasfer thrust from the housing to the shaft when the motor is pulled from the bore-hole or when the bit is held off the bottom of the bore hole during circulation of fluid to flush the bore hole or build up filter cake. Generally, such bearings are provided with springs to absorb the axial shock loading during drilling.
There are many examples of such bearing assemblies in the prior art. In my companion application Ser. No. 068,212, filed Aug. 20, 1979 there is shown a bit clutch operable in a bearing assembly to connect the housing to the shaft for mutual rotation. The clutch is incorporated in a novel bearing assembly which is the subject to the present application.
Bearing assemblies of the type shown in the above-identified patents are subject to severe conditions during use, including high thrust loads and lateral loads, severe shock loading, and the deleterious effects of the erosive drilling fluid. Certain of the prior bearing assemblies have been of the so-called drilling fluid lubricated type U.S. Pat. No. 4,029,368, issued June 14, 1977, to Tschirky and Crase) wherein a portion of the drilling fluid flows through the bearings, between the shaft and the housing, to cool and lubricate the bearings, resulting in rapid erosion of the moving parts. Other bearing assemblies have been sealed U.S. Pat. No. 3,874,818, issued July 15, 1975, to Tschirky and Crase) to enable the bearings to operate in a clean lubricant. Bearings have also been utilized wherein the bearings are adjustably stacked, enabling elimination of manufacturing tolerances, and taking up wear (Crase application, Ser. No. 914,271, filed June 9, 1978 now U.S. Pat. No. 4,198,104.
During drilling operations the severe thrust loads are transmitted to the bit by certain thrust bearings. During off bottom circulation the thrust load is taken by other bearings. The thrust load during application of weight to the bit and the thrust loads caused by hydraulic effects on the motor rotor are both very damaging to the bearings. Unequal load distribution is a problem which can cause excessive wear of certain of the bearings when the other bearings are still useful, resulting in loss of drilling time for service and repair. Unequal load distribution is aggravated in the case of slant hole drilling.
To the extent that bearing parts, in such assemblies, become worn and must be discarded, during service, the cost of such parts is significant. When different parts are employed, the cost of service and repair is increased, due to the need for maintaining an inventory of a large number of replacement parts.